Objective: To determine the construct validity and the internal consistency of the Postgraduate Stressor Questionnaire (PSQ) among postgraduate medical trainees hence it could be used as a valid and reliable instrument to identify stressors among them. Methods: Items of the PSQ were derived from a review of literature on the subject and a discussion with experts in the field. It comprised of 28 items with seven hypothetical groups. The content and face validity was established through discussion with experts from field of Medical Education and Psychiatry. It was administered to all participants (N = 34) of postgraduate personal and professional development programme in a Malaysian university. Data was analysed using Statistical Package Social Sciences (SPSS) version 18. Factor analysis was applied to test construct validity whereas reliability analysis was applied to test internal consistency of the PSQ. Results: Thirty three postgraduate medical trainees participated in this study. Factor analysis found that the 28 items of the PSQ were loaded nicely into the seven predetermined groups as their factor loading values were more than 0.3. The reliability analysis showed that the Cronbach's alpha value for The PSQ was 0.95. Whereas, The Cronbach's alpha values for academic, poor relationship with superior, bureaucratic constraints, work-family conflicts, poor relationship with colleagues, performance pressure, and poor job prospect domains were 0.63, 0.84, 0.81, 0.65, 0.73, 0.78, and 0.70 respectively. Conclusion: This study showed that the PSQ is a reliable and valid instrument to identify stressors of postgraduate medical trainees. It is a promising instrument that can be used in future to explore further on this area.